In order to make solar power a viable alternative to established generating methods such as fossil fuel and nuclear power, it is necessary to bring the manufacturing cost of solar cells down. This has been achieved to some extent in thin film devices by use of large area devices carrying small quantities of silicon, however the manufacturing processes currently formulated for such devices are still complex and lend them selves to farther simplification or streamlining by finding new techniques.
In general, photovoltaic devices have two metal contacts, one of each polarity. In conventional structures one of these metal contacts, usually in a grid formation so as not to shade the semiconductor from too much light, is located on the light receiving or front surface. The second metal contact is located on the rear surface and is the opposite polarity. At the metal/silicon interface, the silicon surface is in general heavily doped above 1×1018 atoms/cm3 so as to enable low resistance contact between the metal and the silicon.
In a less conventional structure, both metal contacts are applied from the same surface. However a challenge in such a device structure is achieving electrical isolation between the n and p regions, particularly when the respective regions are heavily doped (i.e. n+ and p+) to facilitate low resistance contacts.